1. Field of the Invention
The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to an ultrasonic diagnostic apparatus for increasing visibility of an artifact such as a puncture needle.
2. Description of the Related Art
An ultrasonic diagnostic apparatus often performs puncture for puncturing a desired site with a cell needle to obtain a tissue sample for cell tissue diagnosis. At this time, the puncture needle is made of metal and is a specular reflector, and thus when an ultrasonic beam is applied diagonally to the puncture needle, sufficient reflection signals cannot be obtained to make it difficult to visualize the puncture needle.
As shown in FIG. 1, an ultrasonic beam entering the puncture needle at an incident angle θi is reflected in a direction of θr, which makes it difficult to detect ultrasonic echoes with an ultrasonic probe. Generally, scattering occurs at an interface in living tissue, and if the beam diagonally enters the interface, most of ultrasonic echoes return to the ultrasonic probe. On the other hand, scattering rarely occurs at the puncture needle having a smooth surface, and minimal echoes return to the ultrasonic probe. As a result, a sufficient signal amplitude for recognizing the puncture needle cannot be obtained. Particularly, the puncture needle is inserted at various angles depending on test areas, and thus the position of the puncture needle sometimes cannot be checked according to conditions, which is clinically extremely inconvenient.
A conventional technique for increasing visibility of a puncture needle is described in Japanese Patent Application Laid-Open No. 2004-208859. An ultrasonic diagnostic apparatus described in Japanese Patent Application Laid-Open No. 2004-208859 mounts a puncture adapter that can detect an insertion angle of a puncture needle to the puncture needle, obtains information on an insertion angle of the puncture needle, determines a position of the puncture needle in a living body from the information on the insertion angle and a luminance signal based on a received signal of a reflected wave of an ultrasonic beam obtained by an ultrasonic probe, identifies a reflection signal from the puncture needle contained in the received signal of the reflected wave of the ultrasonic beam, and enhances the reflection signal.
Japanese Patent Application Laid-Open No. 2006-175006 describes an ultrasonic observation apparatus that enhances an artifact such as a puncture needle inserted into a body of a patient. The ultrasonic observation apparatus described in Japanese Patent Application Laid-Open No. 2006-175006 performs a processing for enhancing the puncture needle on the basis of a correlation value between a waveform obtained on the basis of an ultrasonic echo generated by reflection from a subject and the puncture needle and a waveform of a reference signal obtained from the puncture needle previously measured in water or the like, or a processing for enhancing the puncture needle on the basis of a result of comparison between an amplitude of the waveform obtained on the basis of the ultrasonic echo generated by reflection from the subject and the puncture needle and a predetermined threshold.